Safety device for a drive unit of a vibration roller

ABSTRACT

The safety device for a drive unit of a vibration roller has a locking bar displaceable between a switch-off position and a locking position and is biased into its switch-off position. The drive unit is forcibly switched off when the locking bar is in its switch-off position. A switch lever is provided for manually operating the drive unit and can be coupled to a toothed rack with a coupling. The toothed rack is connected with a control cable to the drive unit and is biased into a position in which the drive unit is inoperative. A spring biases the coupling into a disengaged position in which the switch lever is disengaged from the toothed rack. The coupling is switchable from the disengaged position into an engaged position for operatively connecting the switch lever and the toothed rack and further into a locked engaged position. A device for blocking the toothed rack and the switch lever in the locked engaged position has a first toothed disk connected to the switch lever and a second disk connected to the locking bar. The second disk has an end face with an elastomer coating cooperating with the teeth of the first disk.

BACKGROUND OF THE INVENTION

The invention relates to a safety device for the drive unit of avibration roller that has a switch lever for manually operation thedrive unit, whereby the drive unit is forcibly switched off when alocking bar is in its switch-off position, from which it can be moved byan operator for operating and driving the roller against a permanentreturn force into a release position.

Safety devices of this kind are known from German Patent 34 42 083 C2.

In the known safety devices the blocking device in a first embodiment iscomprised of a locking pawl that connects the coupling device with thecontrol element and the switch lever in a form-fitting manner to astationary housing as soon as it is moved into the locked engagedposition with the locking bar by the operator. In a second embodimentthe blocking device is comprised of a Hirth toothing one part of whichis fixedly connected with the coupling device and the other part isfixedly connected to the housing whereby both parts, after displacementof the coupling device with the locking bar by the operator into thelocked engaged position, come into contact.

When employing the first mentioned, constructively especially simpleembodiment, the operator must pay close attention that, on the one hand,the normal engaged position of the coupling and not the disengagedposition is adjusted when changes at the drive unit are performed. Thesedifficulties are prevented with the aforementioned second embodimenthaving a blocking device with a Hirth toothing because the operator canmove the switch lever in the engaged position of the coupling with asomewhat increased force expenditure when he slightly releases the forcewith which he supports the locking bar in its release position. Thesecond embodiment however has the disadvantage that it requires anincreased constructive expenditure and allows only a stepwise change atthe drive unit.

It is an object of the invention to provide a safety device according tothe preamble of claim 1 which is characterized by a simple constructionas well as by the possibility of a continuous change of the drive unit.

SUMMARY OF THE INVENTION

The safety device of the present invention is primarily characterized bythe following features:

a locking bar having a switch-off position and a locking position,comprising a first means for biasing the locking bar into its switch-offposition and having an abutment for defining the locking position, thelocking bar displaceable from the switch-off position into the lockingposition for operating the drive unit;

a switch lever for manually operating the drive unit, with the driveunit being forcibly switched off when the locking bar is in itsswitch-off position;

a control element in the form of a toothed rack, the control elementactuated by the switch lever, the control element having a second meansfor biasing the control element into a zero position in which zeroposition the drive unit is inoperative;

an actuating device for the drive unit in the form of a control cableconnected to the control element and the drive unit;

a switchable coupling connected between the control element and theswitch lever, the coupling comprising a spring biasing the coupling intoa disengaged position in which disengaged position the switch lever isfreely movable and disengaged from the control element, and the couplingbeing switchable consecutively from the disengaged position into anengaged position for operatively connecting the switch lever and thecontrol element and further into a locked engaged position with thelocking bar, during movement from the switch-off position to the lockingposition of the locking bar; and

a blocking device comprising a first disk with an end face having teeth,the first disk connected to the switch lever in the locked engagedposition and rotatable with the switch lever, and a second diskconnected to the locking bar having an end face with an elastomercoating oppositely arranged to the end face having teeth, wherein in thelocked engaged position of the coupling the control element and theswitch lever are blocked at least against displacement by the secondmeans for biasing and the spring by the blocking device.

Preferably, the second disk is adjustable relative to the locking bar.The locking bar has a handle portion extending parallel to a guidebracket of the guiding center pole, the handle portion spaced from theguide bracket in the switch-off position and the locking position.

In the inventive safety device the operator must only release the forceexerted for supporting the locking bar in its release position, as isknown from the safety device with the Hirth toothing as a blockingdevice, when he desires to displace the switch lever in the engagedposition of the coupling device for adjusting the drive unit, and he isable to adjust the drive unit in a continuous manner, in contrast to theknown safety device. A slight release movement of the locking bar isalready sufficient in order to be able to move the switch lever with amoderate force expenditure. Furthermore, the blocking device in theinventive safety device is constructively substantially simpler than theknown safety device with the Hirth toothing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in the following with the aid of thedrawings of one particular embodiment.

The drawings show in:

FIGS. 1a and 1b show the safety device from the side in a longitudinalsection in switch-off position of the locking bar with FIG. 1b showingan enlarged segment of FIG. 1a FIGS. 1c and 1d show the safety devicefrom the side in a longitudinal section and showing the locking positionof the locking bar with FIG. 1d show an enlarged segment of FIG. 1c;

DESCRIPTION OF PREFERRED EMBODIMENTS

The safety device according to FIGS. 1 to 4 has a housing 1a, 1b whichis rigidly connected to a vibration roller in the area of a guidebracket 2, whereby of the vibration roller in FIGS. 1a, 1b with theexception of the guide bracket 2, only the end of a center pole 3 formanually guiding the vibration roller is shown to which the guidebracket 2 is connected. A locking bar 4 is pivotably connected to thecenter pole 3 such that it attains an angular position relative to theguide bracket 2 when no force is exerted whereby in this angularposition the remote end 4a is lower than the handle 2a of the bracket 2.As can be seen in FIG. 4, the outer contour of the locking bar 4 ispositioned within the inner contour of the guide bracket 2 in aswitch-off position shown in FIGS. 1a and 3 as well as in any otherposition and its release (locking position, shown in FIG. 1b ) positionin which it essentially extends parallel to the guide bracket 2. Thishas the advantage that the operator cannot jam his fingers between thelocking bar 4 and the guide bracket 2. The locking bar 4 is pivotableabout a pivoting axis. The switch-off position and the further positionsof the locking bar 4 will be explained infra.

The housing 1 has a transverse bore 6 and is connected such to thevibration roller that the transverse bore 6 is above a part 26 of ablocking device connected to the locking bar 4 and explained in detailinfra.

According to FIG. 2, a Bowden cable 8 connected to the drive m, forexample, a hydro pump, of the vibration roller extends into thehousing 1. The Bowden cable 8 is fixedly connected to a toothed rack 9,only schematically shown in the drawing, that is longitudinally slidablewithin the housing 1 and is biased by a second means of biasing in theform of spring 10 abutting against the toothed rack 9 and a housingsurface 13, into an inwardly oriented end position zero position whichis determined by a housing abutment 11.

The toothed rack 9 meshes with a gear wheel 14 which is rotatablysupported at the lower inwardly facing portion of the transverse bore 6(see FIGS. 1a, 1b on an axle 15 which extends downwardly from thehousing 1. At the lower end a first disk 25 is connected to the end faceof the axle 15 and has teeth 25a connected to its free end face that arecoaxial to the axle 15 and which are oppositely arranged to a seconddisk 26 which is form-fittingly but height-adjustably connected with thelocking bar 4. The second disk 26 has on its side facing the teeth 25a acoating 26a of an elastomer material fixedly connected thereto. The gearwheel 14 together with the axle 15 is movable back and forth within thelimits of the housing 1 by the locking bar 4 and has a height such thatit remains in mesh with the toothed rack 9 at all times.

A rotary head 16 is positioned above the gear wheel 14 and is fixedlyconnected to a shaft 17 aligned with the axle 15 which is rotatablysupported within the upper portion of the transverse bore 6 (see FIGS.1a, 1b) and extends past the housing 1 in an upward direction. A switchlever 18 is connected outside the housing to the shaft 17 and extendsperpendicular to the shaft.

Between the rotary head 16 and the gear wheel 14 a pressure spring 19 isarranged which forces apart these two parts in the axial direction ofthe axle 15 and the shaft 17 and forces them into contact with theabutment surfaces 20 of the housing.

Parallel to the axial direction of the shaft 17 two coupling pins 21extend from the free end face of the rotary head 16 toward the gearwheel 14. The gear wheel 14 has two blind holes 22 cooperating with thecoupling pins 21 into which the pins 21 in a predetermined relativeangular position between the gear wheel 14 and the rotary head 16 engagewhen the gear wheel 14 is lifted by the locking bar 4 via the axle 15against the force of the spring 19 toward the rotary head 16. Thearrangement is such that the pins 21 are positioned just outside of theblind holes 22 when the locking bar 4 reaches the lowest positionrepresented in FIG. 1a, i.e., the switch-off position. The gear wheel 14with the blind holes 22 and the rotary head 16 with the pins 21 togetherform a switchable coupling that is actuatable by the locking bar 4 viawhich coupling the switch lever 18 and the toothed rack 9, representingthe control element of the device, can be form-fittingly connected. Sucha connection is achieved by lifting the locking bar 4 from its positionrepresented in FIGS. 1a and 3 whereby initially a normal engagedposition for the following movement between the switch lever 18 and thetoothed rack 9 is reached. By lifting the locking bar 4 further, theteeth 25a are forced into the coating 26a to an increasingly greaterextent due to the increasing counter pressure of the spring 19 and thenfrom the upper abutment 20 so that finally the lever 18 is practicallylocked when the locking bar reaches its upper position, i.e., thelocking position (locking position for the coupling and release position(see FIG. 1b ) for the drive unit).

The safety device according to FIGS. 1a, 1b 4 operated as follows:

In the position of the locking bar 4 shown in FIG. 1a the toothed rack 9is in its initial position zero position under the force of the spring10 in which the Bowden cable 8 turns off the drive unit. The coupling 24is disengaged and the switch lever 18 can be moved without also movingthe gear wheel 14 and with it the toothed rack 9. When the locking bar 4is slightly lifted, the coupling 24 is moved into the normal engagedposition in which the switch lever 18 can be moved in a continuousmanner into any desired drive position needed for the required drivevelocity by engaging the gear wheel 14 and the toothed rack 9. As soonas this position has been reached, the operator lifts the locking barinto its upper end position, the locking position for the coupling inwhich the coupling 24 is locked against rotation and the switch lever 18as well as the toothed rack 9 are blocked in their previously describedposition. When the locking bar 4 is released for any reason by theoperator, it is immediately returned into its initial switch-offposition by its own weight (first means for biasing and also by theforce of the spring 19. Simultaneously, the coupling 24 is disengaged sothat the spring 10 returns the toothed rack 9 due to the freelyrotatable gear wheel 14 into the inward end position zero positionrepresented in FIG. 2 so that the drive unit is switched off by theBowden cable 8. The position of the locking bar 4 represented in FIG. 1ais thus its switch-off position.

For the drive-effecting operation of the switch lever 18 the operatormust first adjust the locking bar 4 into the normal engaged position ofthe coupling 24, but must take care that the pressure between the teeth25a and the coating 26a does not become too great so that the lockingposition is not reached erroneously. This makes it impossible that thelocking bar be simply tied to the guide bracket 2. Furthermore, it isnot attractive for the operator to fix the locking bar in a position inwhich the normal engagement of the coupling 24 is reached because inthis normal engaged position of the coupling 24 the spring 10 exertstorque on the lever 18 via the toothed rack 9 and the gear wheel 14which torque must be permanently countered by the operator for acorrespondingly fixed locking bar 4 while otherwise after completion ofthe adjustment this torque can be avoided by lifting the locking bar 4up to the bracket 2 into its locking position.

By respectively selecting the forces of the spring 10 and 19 it is thuseasily possible to provide a situation in which it is much moreinconvenient for the operator to continuously hold the switch lever 18against a torque than to lift the locking bar 4 into its lockingposition.

Preferably, the disk 25 is adjusted relative to the locking bar 4 suchthat the teeth 25a and the elastomer coating 26a in the switch-offposition of the locking bar 4 have a substantial distance from oneanother.

The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modification within the scope of the appended claims.

I claim:
 1. A safety device for a drive unit of a vibration roller witha guiding center pole, said safety device comprising:a locking barhaving a switch-off position and a locking position, said locking barcomprising a first means for biasing said locking bar into saidswitch-off position and having an abutment for defining said lockingposition, said locking bar displaceable from said switch-off positioninto said locking position for operating the drive unit; a switch leverfor manually operating the drive unit, with the drive unit beingforcibly switched off when said locking bar is in said switch-offposition; a control element in the form of a toothed rack, said controlelement actuated by said switch lever, said control element having asecond means for biasing said control element into a zero position inwhich zero position the drive unit is inoperative; an actuating devicefor the drive unit in the form of a control cable connected to saidcontrol element and the drive unit: a switchable coupling connectedbetween said control element and said switch lever, said couplingcomprising a spring biasing said coupling into a disengaged position inwhich disengaged position said switch lever is freely movable anddisengaged from said control element, and said coupling being switchableconsecutively from said disengaged position into an engaged position foroperatively connecting said switch lever and said control element andfurther into a locked engaged position with said locking bar, duringmovement from said switch-off position to said locking position of saidlocking bar; and a blocking device comprising a first disk with an endface having teeth, said first disk connected to said switch lever insaid locked engaged position so as to be rotated with said switch lever,and a second disk connected to said locking bar having an end face withan elastomer coating oppositely arranged to said end face having teeth,wherein in said locked engaged position of said coupling said controlelement and said switch lever are blocked at least against displacementby said second means for biasing and said spring by said blockingdevice.
 2. A safety device according to claim 1, wherein said seconddisk is adjustable relative to said locking bar.
 3. A safety deviceaccording to claim 1, wherein said locking bar has a handle portionextending parallel to a guide bracket of the guiding center pole, saidhandle portion spaced from the guide bracket in said switch-off positionand said locking position.